Want to really tread hallowed ground?

Maryland commuters have long known that there are only three ways to cross the Potomac between Point of Rocks and the nation's capital. What they don't know is that a century and a half ago, there were more than a dozen.

And they're still there today.

Forget bridges. Think ferries, and especially fords. Throughout history, waterways have exerted profound influences on military campaigns, including the Civil War. These nearly forgotten, but in many cases still scenic and even pristine, crossings along the Potomac River endure as reminders of how and where military commanders dealt with the riverine obstacles confronting their armies.

Many students of the war can easily point out Conrad's Ferry — known today as White's Ferry — where such Confederate commanders as Col. John Mosby, Lt. Col. Lige White and Gen. John McCausland crossed their cavalry. The service still operates a cable ferry named for Confederate Gen. Jubal Early, which regularly floats traffic between Loudoun County, Virginia, and Montgomery County 18 hours a day, weather permitting.

But how many have heard of Rowser's Ford, just a dozen miles northwest of the Capital Beltway? Mosby crossed Rowser's in an attack on the camp of the 6th Michigan Cavalry at Seneca Mills on June 10, 1863. Two weeks later, J.E.B. Stuart's cavalry rode across the Potomac here in its pre-Gettysburg raid on Rockville, which gained the soldiers 150 enemy wagons but deprived Lee of his "eyes and ears" in the war's most decisive battle. Today, the curious will discover Rowser's Ford is still there, a stone's throw from Violette's Lock, No. 24 in the C&O Canal National Historical Park.

Eight miles upriver, the Gettysburg-bound Army of the Potomac began tramping across 1,400-foot-long dual pontoon bridges at Edward's Ferry on June 25, 1863. Two miles downstream, Union Gen. Julius Stahel's cavalry entered Maryland the same day at Young's Island Ford, an obscure and isolated, rarely visited site that halves what is today known as Selden's Island. The Army of the Potomac would require three full days to complete its entry into Maryland.

To access the approach and crossing to Harrison's Island, where Union forces, following Gen. George McClellan's orders for a "slight demonstration" against Leesburg, fought the Battle of Ball's Bluff on Oct. 21, 1861, one has to cross a modern-day Maryland turf farm. A defeat and debacle for the Union, Ball's Bluff would spark the formation of the Congressional Committee on the Conduct of the War.

There are other fords and ferries: Coon's, Great Falls, Spinks, Muddy Branch and Noland's, but the Potomac's most storied crossing is White's Ford. Here, in early September 1862, Robert E. Lee's Army of Northern Virginia waded toward the music of "Maryland, My Maryland" playing from the Free State shore. As Jed Hotchkiss, Stonewall Jackson's mapmaker, recalled, "It was a noble spectacle, the broad river, fringed by the lofty trees in full foliage; the exuberant wealth of the autumnal wild flowers down to the very margin of the stream and a bright green island stretched away to the right."

White's Ford would be crossed and recrossed throughout the war, including five weeks later when Stuart's cavalry, shielded by John Pelham's guns, battled their way back into Virginia after its "second ride around McClellan," and again in July 1864, when Jubal Early retreated after his raid on Washington.

The tradition continues. Each August, near the anniversary of Lee's crossing, several dozen aficionados return to White's Ford, west of Dickerson, to cross — and recross — the Potomac, taking in the scenery and revisiting the "bright green island" that is still there.

If you goCivil War's Potomac Crossings

Gregg Clemmer will lead a Smithsonian tour of the Civil War's Potomac Crossings on Aug. 20, including a crossing of White's Ford. Tickets for the program are available through the Smithsonian Resident Associates at residentassociates.org or by calling 202-633-3030.